Today, the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service issued their final interpretation of the phrase "significant portion of its range" for the purposes of applying the Endangered Species Act (ESA).  This phrase plays a key role in the listing and delisting of species, as it appears in the ESA’s definition of "endangered species" and "threatened species."  Specifically, under the ESA, an "endangered species" is defined as "any species which is in danger of extinction throughout all or a significant portion of its range[,]" and a "threatened species" is defined as "any species which is likely to become an endangered species within the foreseeable future throughout all of a significant portion of its range."  16 U.S.C. 1532(6) & (20).  The accompanying announcement issued by USFWS states that under the new policy, which does not go into effect until July 31, 2014, a species could be listed "as threatened or endangered throughout its range if the best available science shows that the species is threatened or endangered in a vital portion of that range, the loss of which would put the species as a whole at risk of extinction."  The announcement also states that the "policy clarifies a species’ ‘range’ as the geographical area within which that species is found at the time of the listing determination."  The website for the USFWS states that during the interim period between now and the policy’s July 31 effective date, the USFWS "will consider the interpretations and principles in [the] final policy as nonbinding guidance in making individual listing determinations."